Human factors aspects of using head up displays in automobiles: A review of the literature: Interim report

Abstract

This document provides an overview of studies investigating the use of head-up displays (HUDs) by aviators and drivers, including a summary of HUD research variables, test procedures and study results. The predicted performance advantages of automotive HUDs include increased eyes-on-the-road time and reduced reaccommodation time, particularly for the older driver. To date, the research does not provide robust evidence for operationally significant performance advantages due to HUDs. However, conclusions are equivocal due to the interaction of independent variables such as workload, display complexity and age. Studies indicate that key operator performance issues with HUDs include contrast interference, where HUD symbology masks safety-critical targets in the forward driving scene, and cognitive capture, or degradation of responses to external targets due to the processing of information from a HUD image. In general, the review supports and extends earlier findings that HUD information cannot be processed separately from external roadway information. Countermeasures reviewed in this paper include the use of conformal symbology, and auditory HUDs. The review identifies a number of implementation issues for automotive HUDs: (1) reliable measures of the effect of HUD use on responses to priority external targets must be obtained, under realistic operating conditions; (2) practical considerations of cost, size, and adaptability to a range of driver eye heights figure prominently if the use of HUDs in the private vehicle fleet in the U.S. is to become routine; and (3) driver age and associated visual/cognitive performance differences which are commonly linked to safe vehicle operation must be taken into account during product design, development, and testing.